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Abstract: Mid-infrared absorption spectroscopy was applied to the detection of the hydroperoxyl radical (HO2) in pulsed laser photolysis combined with a laser absorption kinetics reactor. The transition of the ν 3 vibrational band assigned to the O–O stretch mode around 1065cm−1 was probed with a thermoelectrically cooled, continuous wave, mid-infrared, distributed feedback quantum cascade laser (QCL). The HO2 was generated through 355nm photolysis of Cl2/1,4-c-C6H8/O2 mixtures. The mid-infrared absorption spectrum of the HO2 radical was recorded between 1064 and 1065.5cm−1. The absorption line shapes were well represented by the Voigt profile. The nitrogen-broadening coefficients of the HO2 radical at 295K were determined for four absorption lines around 1065cm−1. Mid-infrared absorption detection using a QCL as a spectroscopic light source is a powerful method in spectroscopic and kinetics studies of the HO2 radical. [ABSTRACT FROM AUTHOR]

Abstract: The line shape profiles of the 000–000 band of hydroperoxy radical (HO2) have been measured in the presence of nitrogen and water using laser photolysis/cw near infrared two-tone frequency modulation spectroscopy. On the basis of the theory described by Avetisov and Kauranen [Appl. Opt. 35 (1996) 4705], the absorption line shapes were well represented by the Voigt profile. The nitrogen- and water-broadening coefficients for the 7020.766cm−1 161,16←160,16 F1 line of HO2 were estimated to be 0.101±0.013 and 0.216±0.133cm−1atm−1, respectively. The large value of water-broadening coefficient suggests the long range interaction between HO2 with water. [Copyright &y& Elsevier]